A multiple wavelength light source generates an output signal having a comb of accurately spaced apart frequencies with variable free spectral range in the C-band of optical fiber communication. Overlapping the first and second plates to define a widened seam bounded at least in part by the elongated edges of the respective plates, and welding along the elongated edge of the first plate to join the elongated edge of the first plate to an adjacent surface of the second plate. Other embodiments may be described andor claimed. The continuous contact may be caused by a selecting element comprising, for example, a stylus or a digit of a subject.